Richard Bogren | 9/7/2018 1:49:17 PM
By Dan Gill
LSU AgCenter Horticulturist
(09/07/18) We often hear Labor Day called the traditional end of summer, and, according to the calendar, fall will officially start at the autumnal equinox on Sept. 22. We know good and well, however, that our Louisiana summer season extends quite a while longer.
But if you take the time to notice, the weather is beginning a subtle shift away from the intensely hot, stressful weather of midsummer. When you walk outside in the morning, the air feels just a bit more comfortable. The days are getting shorter, and that is beginning to have an effect. Perhaps it’s just wishful thinking, but if you squint just right, you can almost see the end of our long and brutally hot summer.
The word “fall” commonly conjures up images of harvest, falling leaves, the end of the growing season and the beginning of plant dormancy leading into winter. For gardeners in Louisiana, however, the traditional fall period is not a time of winding things down in the garden but of revival and renewed effort. Finally, we can get back into our gardens and enjoy ourselves as the debilitating heat of the hot season loses its grip on the weather.
For the next two months we will experience a gradual shift to milder weather. There will be cool spells followed by decidedly hot summer-like weather. But as we move into late October, cooler weather will begin to dominate the scene. Not until mid- to late November do we generally experience the nippy cold weather and changing leaves that tell us that fall has finally arrived.
You might begin to notice an increase of vigor in your warm-season bedding plants in September. Even heat-tolerant flowers do not always look their best in August. But shorter days mean fewer hours of intense heat, even though the daytime highs may stay about the same, and plants begin to experience less stress. This encourages a “second wind” in the flower garden that may last well into October or early November.
Given this, consider cutting back some of your summer bedding plants and flowers that have grown tall and leggy over the long growing season. This is done in August or early September at the latest, and generally involves cutting plants back about one-third to one-half their height.
While you’re at it, it might be a good idea to impose some order on those overgrown flower beds. In addition to cutting back, groom the planting to remove dead flowers and unattractive foliage. If plants are leaning or have fallen over onto nearby neighbors, prop them up or stake them so they will stand upright. Just about every year about this time I find the remains of some unfortunate plant that was overwhelmed when some larger, more vigorous nearby plants leaned over it.
If you have an area where the summer flowers finished and have been removed, it is still too hot to plant most cool-season bedding plants. Mulch the area now, and wait until the more reliably cooler weather of October or November to plant the beds with cool-season bedding plants like pansy, viola, dianthus and snapdragon.
If you haven’t done so, cut back your repeat-flowering rose bushes, including such popular groups as hybrid tea roses, grandiflora roses, floribunda roses, miniature roses, polyantha roses, Bourbons, teas, Chinas and English roses, to name a few. Many old-fashioned climbers, ramblers, Lady Banks roses and some bush roses that bloom heavily in spring to early summer then stop will bloom next year on the growth they made this summer. They should not be cut back now.
It is too early to plant hardy trees, shrubs, ground covers and vines in the landscape. Temperatures in the 80s and 90s will likely be common in September, and this is still too stressful for new plantings. Wait at least until the cooler weather of October. The ideal planting season for hardy trees, shrubs and ground covers is November through February.
Spring-flowering bulbs, such as tulips and daffodils, generally become available at nurseries this month. But there is no hurry to plant them. Purchase them if you like while the selection is good, but wait to plant bulbs into the garden from mid-October through early December.
The chrysanthemum is often considered the floral symbol of fall, and you will begin to see them available for sale this month as well. Folks, it ain’t fall yet. When planted in the garden while daytime highs are still in the upper 80s and lower 90s, the flowers will rapidly wither in the heat. Wait until reliably cooler temperatures to purchase chrysanthemums, and the flowers will last longer in the garden and provide a longer colorful display. Other plants popular to use in fall displays include ornamental peppers, crotons, ornamental gourds and pumpkins.
So let’s anticipate the soon-to-arrive (we hope) milder weather, and enjoy the delights of gardening during the next few months. But when the fall equinox arrives later this month, don’t get carried away. For us, summer will still be lingering for a while after.
Deadheading spent flowers from bedding plants not only encourages repeat blooming but also enhances the appearance of the plant. Photo by Rick Bogren/LSU AgCenter
Vinca is a drought-tolerant bedding plant that requires lesser amounts of irrigation. LSU AgCenter archive photo by Allen Owings